This usually occurs after you have dropped off into a help position and the ball is passed or reversed quickly to your man.
Unfortunately, when a shooter is wide open you can’t just run at him or he will usually wait until you have over-committed and dribble right past you for a layup.
The only real solution is to execute a proper closeout. To do this correctly you must begin closing out as the ball is being passed and is in the air.
If you wait until the ball is caught by a skilled offensive player you will have no chance of stopping him from getting off a good shot.
Once the ball is in the air you should sprint two thirds of the way towards the shooter and then break down into short, choppy steps.
These choppy steps will stop your momentum, slow you down and allow you to regain your balance while re-establishing your defensive stance. (You should always be able to hear a good closeout so if your shoes are squeaking then you are probably doing it right.)
At the same time your shoes are squeaking, throw your hands up over your head to immediately stop the shot and/or the quick entry pass.
Even though your hands are up you need to stay as low as possible in order to be in a position to stop any possible drives.
Once you have stopped the outside shot and the drive to the rim you can readjust your positioning once again and play your normal on ball defense.